Calculating watts/kg from VAM

Discussion in 'Power Training' started by Watoni, Nov 14, 2009.

  1. Watoni

    Watoni New Member

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    I have thrown down a few public challenges to help me with my goal of slimming down and getting fit.

    One is to break one hour on Mt. Diablo in Northern California (South Gate).

    It seems people analyzing pro climbing performances have used a formula to estimate watts/kg.
    Relative power (W/kg) = VAM (m/hour) / (Gradient factor x 100)
    Gradient factor = 2+(percentage grade/10), so 6% would be 2.6

    Since Mt. Diablo is over an hour from where I live, I was hoping to use this to guesstimate what watts/kg I will need (and I am intersted what folks think of the formula, which could be useful for estimating requirements for hills outside your area).

    So, if the climb is 11.3 miles at 5.8% average, it is 981.5m to the top. If the goal is just under an hour, I need to climb at least 982m/h.

    According to the above formula:
    982/((2+0.58)*100)= ~3.8w/kg. Honestly that does not seem too hard, though I am not sure I can do that for an hour at the moment.

    I have not gone all out recently (trying to get lots of SST in), but I did do a recent effort on a 3.3 mile, 7.3% hill (Old la Honda) in a group so I went a bit harder than normal and did 21 minutes, so more like:
    VAM:393/(21/60)= 1123
    1123/273= 4.11 watts/kg

    My feeling is that breaking one hour on Diablo is more of a challenge than this or even breaking 20 minutes on Old la Honda (I did just under 20 a few years ago when I was slimmer). If this math is correct, though, that should not be the case and my goal should be attainable now?

    Any views on this formula or the watts/kg required for Diablo?

    Thanks!
     
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  2. dhk2

    dhk2 Active Member

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    Haven't seen your formula before. Here's the simpler one I can remember for low-speed climbing (eg, 12 mph and under) when air resistance is small:

    Vmeters/sec (vertical rate of climb) x kg (mass of bike+rider) x 10 (nts/kg)= nt-m/sec (watts). Add a fudge factor for tire resistance, aero drag, maybe 60 watts for 10-12 mph to get the power you need to apply to the pedals.

    So, for your example of climbing 982 meters vertical in an hour, just divide 982 by 3600 (secs/hour) to get .273 m/sec (Vroc). If you weigh 80 kg, and all the rest weighs 10, that's 90 kg. Note the gradient doesn't matter, just the meters/second vertical. Doing the multiplication:

    .273 x 90 x 10 = 246 watts + 60 watts (tire and aero drag) = 306 watts total output

    Then, for watts/kg, 306/80 = 3.825 w/kg. Hey, that's close to your number :)
     
  3. RChung

    RChung New Member

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    I have 11.37 miles and 3365 feet from the Athenian School to the top of Diablo, and 3.37 miles and 1290 feet from the bridge to the stop sign for OLH.

    In zero wind conditions, OLH in 21:00 minutes demands almost exactly the same watts/kg as Diablo in 60:00 minutes -- but there's rarely zero wind on Diablo.
     
  4. lanierb

    lanierb New Member

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    I've done both OLH and Diablo a bunch of times so I can help a bit.

    First, if you can do OLH in 21 and you're in decent shape (so you don't die half way up Diablo), you should easily do an hour on Diablo -- I would guess around 59:00 or so. I have several data points (different people) on that.

    Also, I've done Diablo a bunch of times in under an hour, and just looking back through my data I see twice when I did it within 10 seconds of an hour with only 3.6 w/kg (PT watts, 2 different PT's). These were both carrying no patch kit and no water and using my lightest wheelset (Zipp 303 tubulars), and going with a group so getting a draft here and there, so view it as best case scenario.

    Bottom line is you're ready for it.
     
  5. DancenMacabre

    DancenMacabre New Member

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    UGGGGGHHH! Rub it in why dont you, making 3.8 sound like kids stuff :(

    Still working on 1:20 from the north side *hangs head in shame* :eek:
     
  6. midlife

    midlife New Member

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  7. Watoni

    Watoni New Member

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    Je parle francais comme une vache espagnole ...

    Hey, DM, just being optimistic on the challenge. I thought it would be more like 4+ watts/kg, so 3.8 is easy only by comparison.

    Plus, you are aspiring to an FTP of 300 watts and are not chunky like me at present, no?

    Let's both break the 20/60 minute barrier ...
     
  8. swampy1970

    swampy1970 Well-Known Member

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    Keep at it and your power and ability to suffer will increase.

    Mental fortitude on a climb like that comes in very useful - the amount of time you can lose going uphill because of a wandering mind and the thoughts along the lines of 'feck me this hurts' whilst looking at the countryside for some kind of inspiration, is actually quite alarming.

    Watch how the fast lads climb - even when they're suffering a thousand deaths they still look smooth and relaxed... unless you just happen to be watching old videos of the Columbian Fabio Parra.

    Sure, use a big gear but never use one that's forces you to lose fluidity. Experiment with different gear sizes for a given speed. Most people can't pedal like Lance did when he was seated.
     
  9. DancenMacabre

    DancenMacabre New Member

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    Watoni, me chunky? Bmi is around 21-22 but I guess i am another fattie girl compared to most women who race. KA I think is like bmi = 19.5

    300 watts? Yea, yea, in my dreams!!!

    Good luck getting up the mountain in 1 hour. From the numbers in that formula you are already good for 1 hour. Now go get climbing ;)

    Swampy, I likes the climbing but me no good at it :D:D:D:D

    Yea I do like the climb (for real). It is pretty, low traffic - super good workout.

    Guess the w/kg thing bites me in the but though at a wheezing 3 - pretty much because of weight loss but not some big power gain
     
  10. bbrauer

    bbrauer New Member

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    This had me thinking about a local off-road climb I've been doing for years (Harding Truck Trail...it just re-opened after being closed due to fires). My best time is 1:01, and obviously I'd like to break the 1 hour mark. Aside from a "fudge factor" for off-road rolling resistance, what's a good estimate for establishing a standard between off-road RR and on-road?
     
  11. Watoni

    Watoni New Member

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    Silly, chunky was a reference to me, not you!
    You have done the tough part, now train ... Diablo is going down
     
  12. lanierb

    lanierb New Member

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    I'm jealous. I just love 1 hr of all out pain! There's nothing like it. Since I moved east it's not as easy for me to access stuff like that.
     
  13. swampy1970

    swampy1970 Well-Known Member

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    You can't deny that a good w/kg is required to go up a hill fast but on the flip side you can also see many riders who are able to put out big numbers on the flat for seemingly endless miles who'll turn into shrinking violets as soon as the hills show up.

    I can remember a phrase that my old coach said in passing once that for some reason stuck with me - "you shouldn't mind because when you're done the pain really doesn't matter." I can't remember what the context was but it just sticks in my head like an old broken record when the going starts getting really tough.

    Have fun on Diablo. Make it hurt lots and reward yourself with that view from the top... Ride down and do it again.
     
  14. swampy1970

    swampy1970 Well-Known Member

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    Call me old school, but who the hell goes out on carbon rims with no water and no saddle bag on a mountain like Diablo in training?

    At the very least it's an hour long effort - you need water. Those few grams that you save from 1/2 a bottle pale into insignificance to the power of dehydration...
     
  15. lanierb

    lanierb New Member

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    Who said it was in training?
     
  16. swampy1970

    swampy1970 Well-Known Member

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    I've been looking for races up there and failed miserably... so I assumed it was training.

    If you'd be so kind as to inform poor Swamps as too when races do go up there I'd be most grateful.
     
  17. Alex Simmons

    Alex Simmons Member

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    Wouldn't matter in any case, the performance degredation of under hydration will far outweigh the benefit of reduced mass on a long climb. Funny enough, I was just talking with the sports science peeps in Adelaide about their research on this very topic.
     
  18. lanierb

    lanierb New Member

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    There are two races up Diablo every year that I know of. One is in July or so and is a USCF race. The other is the first Sunday in October and is run by a local organization (Save Mt Diablo or something like that -- google it). They're both good. In the October one they close all the roads even to pedestrians/bikes so you can cut corners etc and generally just concentrate on going fast so that's pretty cool, and the last 3-4 years they have also had timing chips (anklets) for accurate timing. It's a fun race.

    It's a one-hour hill climb (about 12 miles) in cold enough weather that you wear a jacket up until about 60 seconds before they blow the horn. I guess I felt that I didn't really need water in those conditions, but I suppose I could be wrong. In similar conditions I typically use less than one bottle of water over about 3-4 hrs on weekend rides (despite carrying two), but I suppose I could be messing that up as well.
     
  19. sharonk868

    sharonk868 New Member

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    Thanks you for the post.
    Hi guys, Im a newbie. Nice to join this forum.
     
  20. swampy1970

    swampy1970 Well-Known Member

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    I very cold weather I'd use 2 bottles in 3 hours but you don't really get that "very cold weather" in sunny NorCal unless you're setting off at 5.00am during the winter months. If you're racing up Diablo and it's warmish I'd take ~1/2 a bottle.
     
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